This invention relates generally to carbon dioxide (“CO2”) sequestration and more particularly to apparatus and method for carbon dioxide sequestration using a mobile concrete mixing apparatus.
Anthropogenic carbon dioxide is being viewed as a pollutant with respect to its contribution to the levels of greenhouse gases in the atmosphere. There are many anthropogenic sources of carbon dioxide including the burning of carbonaceous fuels and the manufacture of cementitious materials containing calcium oxide using materials containing calcium carbonate as the raw material.
It is known that carbon dioxide may be sequestered by mixing carbon dioxide with a concrete premix. The carbon dioxide chemically reacts with the calcium oxide or calcium hydroxide phases in the concrete and forms calcium carbonate. For example, U.S. Pat. No. 8,272,205 to Estes et al. describes a method for sequestering carbon dioxide in a concrete mixing truck.
It is also known that the hardening or curing of cement-containing materials can be accelerated by carbonation in which calcium hydroxide in the cement is transformed into calcium carbonate by absorbing carbon dioxide.
The exhaust gas temperature of internal combustion engines can reach high temperatures, for example about 600° C. (1100° F.). Mixing gas at such high temperatures could lead to concrete curing faster than desired. While the process described in the '205 Patent mentioned above is effective to sequester carbon dioxide, it does not specifically provide for control of the curing rate of the concrete.
Accordingly, there remains a need for an apparatus and method for sequestration of carbon dioxide in a mobile concrete mixing apparatus while controlling the curing rate of the concrete.